The day before yesterday, my daughter complained that there were too many mosquitoes in the evening self-study, so she went to Jianhu RT-Mart to buy mosquito repellent, and chose to buy a potion containing mosquito repellent. The bottom with a red label “slightly toxic”. Other varieties are not. I tell you today why I buy toxic mosquito repellent. The active ingredient of this repellent is N, N-diethyl-m-toluamide, abbreviated as DEET, also known as mosquito repellent in China. It was developed by the U.S. Army during World War II, presumably for the needs of combat in the tropical jungle. However, when it was successfully developed (1946), World War II had already ended, and it was put into civilian use in 1957. The technique of making mosquito repellent is simple, low cost, low toxicity, and extremely effective in repelling mosquitoes, and soon became popular. About one-third of Americans have used mosquito repellent, and by now it has been used about 9 billion times. More miraculous is, mosquitoes have been used for more than 50 years, mosquitoes actually have not developed resistance, the effect of mosquito repellent does not decrease, and is still the only one recommended by the U.S. Centers for Disease Control personal mosquito repellent. The U.S. market for mosquito repellents, or mainly mosquito repellent amine. If there was a patent on mosquito repellent, it has long expired, and manufacturers who have the conditions can produce. Strangely enough, although there are many repellents on the domestic market, but it is difficult to find pure mosquito repellent products, either claiming to be a new generation of mosquito repellent, mainly repellent esters (called IR3535 abroad); or claim to be pure natural ingredients, especially Chinese herbal ingredients. Even with mosquito repellent ingredients, but also often add Chinese herbal ingredients, both increased costs, but also increased health risks. Some products specifically emphasize “no mosquito repellent”, so that consumers have a bad impression that containing mosquito repellent is a bad toxic products. Then the toxicity of mosquito repellent amine how exactly? The U.S. Environmental Protection Agency in 1998 had a comprehensive assessment of the safety of mosquito repellent amine, that the toxicity of mosquito repellent amine is very low, not found to be carcinogenic, mutagenic, developmental toxicity, the general population does not pose a health threat. From 1960 to that time, there were 14 reported seizures in the United States after the use of mosquito repellent, mostly in children, including four deaths. However, it is not certain that mosquito repellent is a factor in seizures; it is possible that it is just coincidental: 15,000 to 20,000 children in the United States develop non-febrile epilepsy each year, and about 17 million children use mosquito repellent 10 times a year, so the possibility exists that seizures happen to occur after using mosquito repellent. The EPA estimates that the probability of a mosquito repellent user developing epilepsy after using mosquito repellent is 1 in 100 million. So mosquito repellent is very safe and can be used by children (the American Academy of Pediatrics simply recommends against use in infants less than 2 months old). In contrast, other new generation repellents, “all-natural” products that are trying to replace mosquito repellent have not been evaluated as thoroughly as mosquito repellent. Moreover, they are not effective in repelling mosquitoes. The New England Journal of Medicine published in 2002, the experimental report pointed out that the market for mosquito repellent products only contain mosquito repellent amine (DEET) can play a role in mosquito repellent, its effect and concentration, 23.8% concentration of mosquito repellent 302 points, 20% concentration of mosquito repellent 234 points, 6.65% concentration of mosquito repellent 112 points, 4.75% concentration of mosquito repellent 88 points. Other products that want to replace DEET are foolish, for example, 7.75% repellent ester (IR3535) can only repel mosquitoes 23 points, 2% of soybean oil can only repel mosquitoes 95 points, 10% of citronella oil can only repel mosquitoes 20 points. Mosquito repellent amine should be sprayed onto bare skin or clothing to be effective, if you just wear a rubber band containing mosquito repellent amine on your hand, it is not effective. Mosquito repellent amine can be absorbed into the body through the skin, for insurance purposes, do not over spray, do not use where the skin is damaged; do not spray directly to the face, but first spray to the hands and then wipe to the face; there is no need to repel mosquitoes should be washed in time. The lower the concentration of mosquito repellent is not the less likely to be absorbed into the body. Quite the contrary, because the organic solvent used to dilute mosquito repellent amine is more likely to penetrate into the skin, low concentration of mosquito repellent amine but more easily absorbed by the body. For example, 15% of mosquito repellent products are absorbed into the skin at a rate of 20%, while undiluted mosquito repellent is absorbed into the skin at a rate of 12%. Why is mosquito repellent so effective? What is its mechanism? Research in this area is just beginning, there is controversy. Some studies believe that mosquitoes have a receptor on the antennae can feel the body emitting an organic substance, mosquitoes use to find human skin under the mouth, and mosquito repellent can bind with the receptor to inhibit its activity, so that the mosquitoes immediately lost the target of attack. Some studies believe that the mosquito tentacles have a special receptor that can feel the mosquito-avoidance amine, and mosquitoes do not like the smell of mosquito-avoidance amine, was driven away.